1. Field Of The Invention
The invention relates to a process for the production of threo-4-alkoxy-5-(arylhydroxymethyl)-2(5H)-furanones of the formula: ##STR1## wherein R is a phenyl group optionally substituted by one or more halogen atoms and/or lower alkyl groups and/or a nitro group and R.sup.1 is an alkyl group with 1 to 4 carbon atoms. The configuration represented in formula I is to be viewed as a relative configuration; it also comprises the mirror image of the reproduced formula.
2. Background Art
Threo-4-alkoxy-5-(arylhydroxymethyl)-2(5H)-furanones are pharmaceutical active ingredients, known from West German 0S 3615157, with anticonvulsive or antiepileptic activity. They were previously produced in a multistage synthesis from the enol ethers of .beta.-oxocarboxylic acid esters, for example, (E)-3-methoxy-2-butenoic acid methyl ester, and the corresponding benzaldehydes (West German OS 3615157). This synthesis did stereospecifically yield the desired threo configuration, but it is complicated and the total yield is small.
It is known that the 5-lithio derivatives of 4-alkoxy-2(5H)-furanones (=tetronic acid alkyl esters) can be condensed with aromatic aldehydes to 4-alkoxy-5-(arylhydroxymethyl)-2(5H)-furanones [A. Pelter et al., J. Chem. Soc. Perkin Trans. I, (1987), page 717]. For the production of the 5-lithiotetronic acid esters, the tetronic acid esters were reacted with lithium diisopropylamide or n-butyllithium under protective gas at -78.degree. C., which is hardly acceptable for a production on an industrial scale for cost and safety reasons. Also, the condensation with the aldehydes was performed under these conditions. Mixtures of threo and erythro diastereomers, whose separation is often difficult, were constantly obtained as products.